Iran imported weapons worth over £350 million in the space of three years
despite being the target of a United Nations arms embargo, Oxfam will
disclose on Thursday.

In all, 10 countries subjected to arms embargoes still managed to buy weaponry worth over £1.4 billion between 2000 and 2010.

Their success in tapping the international arms market showed the ineffectiveness of current restrictions, said Anna MacDonald, the Control Arms campaigns manager for Oxfam. She added: "If you are an unscrupulous government, it's quite easy to find your way around them."

The UN Security Council urged all member states to "exercise vigilance and restraint" in the supply of arms to Iran from 2007 onwards. But data from the Stockholm International Peace Research Institute suggests the country's rulers went on to buy weaponry worth £350 million by 2010.

Russia and China, who prevented the UN from imposing a comprehensive embargo, are understood to have been the principal suppliers.

Azerbaijan, which will host the Eurovision song contest later this month, is subjected to an arms embargo by the Organisation for Security and Cooperation in Europe, an association of 56 states. Nonetheless, the country imported arms worth over £450 million between 2000 and 2010, making it the biggest purchaser of weaponry by any nation under embargo.

"One of the reasons why embargoes don't work is there are no global rules on the conventional arms trade," said Ms MacDonald. Individual countries are free either to restrict their exports or sell weapons to any buyer – and the figures demonstrate that even governments subjected to embargoes are skilled at evading them.

Campaigners say the solution would be a global treaty regulating the trade in conventional weapons. Britain already forbids any exports that could be used for "internal repression" or "external aggression". A new treaty could take those restrictions and make them global.

The UN will hold a conference to discuss the issue in July. However, countries like Russia and China benefit greatly from arms exports. They are highly unlikely to accept any international rules that would restrict this trade.